Photosynthesis Part 1 Chapter 10 Pages 185 199 Absorbing light Light Reactions Energy Harvested Preview Review Energy Matter Redox RXNS Laws of Thermodynamics Kinetic VS Potential Energy Follow Carbons Follow Electrons Carbon Cycle Electron transport chain chemiosmosis ATP synthase Exergonic release of energy Enderogonic taking in of energy Photosynthesis is Endergonic Thylakoid disk structure arranged in a stack They have a membrane which causes two compartments Stroma outside the Thylakoid space Thylakoid Space is inside the thylakoid Nature of light Form of energy on electromagnetic spectrum from 380 750 nm Both particle and wave properties Wavelength distance between crests Inverse relationship with inverse to wavelength o Shorter wave more energy Chlorophyl is just one of many pigments that organisms have Pigments substances that selectively absorb visible light Chlorophyl A o Chlorophyl B o Carotenoids The rate of photosynthesis DOES change over different wavelengths What happens to absorbed light Photon hits pigment e excited then falls Dissipation fig 10 11 o Emit Photon of light Fluorescence o Emit heat o Transfer e to other pigment Resonance transfer Electron Transport chains are series of Redox Reactions Light Reactions Converting solar energy to chemical energy 1 Light harvesting complexes PSII and PSI a Within thylakoid membrane b Contain proteins and few 100 pigments c Outer pigments absorb purple wavelengths inner absorb red d Excited e energy transferred via resonance transfer from high E low E 2 LINEAR ELECTRON FLOW PRODUCES ATP AND NADPH a Photons excite e in pigments and energy transferred to pair of chlorophyll a P680 donates e to a primary acceptor in the reaction complex b P680 strongest oxidizing agent in the world c Rips 2 e from WATER not light d Water donates 2 e to excited P680 one by one e E fall down e transport chain via redox rxns to PSI e acceptor P700 f Additional photons excite these eg Cytochrome complex in 1st e chain pumps H into thylakoid space WHAT WILL THIS DO i Supplies the gradient to fuel the ATP Synthase and create ATP h Excited e form P700 fall down 2nd e transport chain via Ferredoxin fd to electron shuttle NADPH 3 Cyclin electron flow Produces ONLY ATP Damage control mechanism a Uses PSI Fd Ferradoxin cytochrome complex b Creates proton gradient ATP synthases Chapter 10 Pages 198 203 Calvin Cycle Photorespiration Overview of Calvin Cycle What does cycle mean o Something needs to be regenerated What is C input C output What types of energy are used Is it catabolic or anabolic anabolic process Following NET synthesis of ONE G3P Need 3 turns of the cycle for one G3P Melvin CALVIN Cycle Important because the sugars are made in this cycle 1 PHASE 1 CARBON FIXATION a 3X CO2 5 C RuBP 6 C 2 3 C b Rubisco most abundant enzyme on earth 2 PHASE 2 REDUCTION a Input ATP 6ATP 3 cycles b Input 2e 6NADPH NADP 3 cycles c Output 1 3 C G3P 3 PHASE 3 REGENERATION of RuBP CO2 acceptor a 5 3 c rearranged to 3 5 C RuBP b Input 3 ATP 3 Cycles How many ATP NADPH required to make 1 glucose 18 ATP and 12 NADPH Two cycles because glucose has 6 carbons Photorespiration An evolutionary relic that causes problems Ancient Atmosphere o Before photosynthesis A lot more CO2 a lot less O2 o Cyanobacteria 1st to photosynthesize 2 7 billion years ago Ancient Atmosphere Rubisco can bind CO2 OR O2 When Rubisco Ribulose bisphosphate carboxylase oxygenase o Rubisco W CO2 2 3 carbon phosphoglycerate o Rubisco O2 1 3 phosphoglycerate and 1 2 carbon compound Why is this a problem o Releases CO2 o Uses ATP in the Process o Decreases photosynthesis output by 25 50 C4 plants Change in place Includes many grasses Anatomical adaptations Mesophyll cells fix carbon to 4 C compound Bundle sheath cells release CO2 and proceed w Calvin Cycle Need to invest energy to make system work Bundle sheath only have PSI so only carry out cyclic e flow CAM PLANTS Change in time includes succulents cacti pineapple etc Timing adaptations o Stomata open night ONLY o Fix CO2 into organic acids During day CO2 release and used